Expandable metal-pipe bonded body and manufacturing method...

Pipes and tubular conduits – Combined – With end structure

Reexamination Certificate

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Details

C138S155000, C138S171000, C138SDIG001

Reexamination Certificate

active

06405761

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an expandable metal-pipe bonded body and a manufacturing method thereof, and more particularly, to an expandable metal-pipe bonded body well adaptable for plant pipes and line pipes, which are used in chemical industry and petrochemical industry, and oil-well tubes, such as casing tubes, production tubes, and coiled tubes, which are used in the oil well, and a method of manufacturing such an expandable metal-pipe bonded body.
2. Description of the Related Art
Long metal pipes have been used for a long distance transportation of corrosive fluid in the fields of chemical and petrochemical industries. The pipe line is used for transporting crude oil from an oil field to a refinery, and its length ranges into several tens Km.
To drill an oil well, a steel pipe, called a casing, is inserted into a bore hole in order to protect the bore hole drilled in the ground and to prevent crude oil from leaking. The oil well is located usually several thousands meter under the ground. Therefore, it is required to use a casing of several thousands meter long.
A seamless steel pipe of good corrosion proof is generally used for the metal pipe exposed to a corrosive atmosphere. The seamless steel pipe mass-produced is 10 to 15 m long, and the longest seamless steel pipe that can be manufactured is approximately 100 m at most. For this reason, a pipe bonded body as a string of seamless steel pipes of 10 to 15 m long is used for the line pipe or the oil-well tube, such as a casing.
A screw connecting method (mechanical bonding method), a welding method (orbital welding method), and a diffusion bonding method are typically known for the bonding method of bonding those metal pipes applied to such a use.
It is a common practice that a pipe bonded body formed by bonding a plurality of metal pipes of a given length in series (referred to as a metal-pipe bonded body) is used as intact or without increasing or decreasing the inside diameter of the bonded body. A metal-pipe bonded body having a desired inside diameter is generally formed by bonding metal pipes of the desired inside diameter in a string.
The casing for the oil well is buried in the ground, while the line pipe is laid on the ground. Accordingly, if the metal-pipe bonded body of a given inside diameter, while not altered, is used for the casing, the following problem arises.
It is technically difficult to dig into the earth toward an oil well laid several thousands under the ground in a state that the bore hole dug remains naked. For this reason, the oil well drilling work is done while repeating the following three steps: a first step of drilling a bore hole in the ground by use of drill pipe with a bit attached atop it, a second step of inserting a casing into the bore hole to protect the dug bore when the bore reaches a certain depth, and a third step to fix the casing by pouring cement into the gap between the inserted casing and the stratum. As a result, a plurality of casings are telescopically bonded in the oil bore.
A typical structure of the oil well is illustrated in FIG.
6
. An oil well
10
exemplarily shown in
FIG. 6
is constructed with four casings; a conductor pipe
12
, a surface casing
14
, an intermediate casing
16
, and a production casing
18
. The conductor pipe
12
has the largest outside diameter and functions to protect the bore wall located in the vicinity of the land surface. The surface casing
14
is telescopically inserted into the conductor pipe
12
. The production casing
18
, which is the longest of those casings, ranges to an oil stratum.
When the second casing (referred to as an “inside casing”) is inserted into the oil bore through the first inserted casing (referred to as an “outside casing”) (the first casing=first inserted casing, the second casing=subsequently inserted casing), the inserting of the second casing into the first casing is difficult when those casings are not aligned with each other axially or either of those casings is irregular in shape. To avoid this disadvantage, it is necessary to select the outside diameter of the inside casing to be smaller than the inside diameter of the outside casing by 10 to 30%.
A production efficiency of the oil well depends on the inside diameter of the production casing ranging to the oil stratum. To secure a given production efficiency, it is necessary not only to set the inside diameter of the production casing at a predetermined value, but also to set the inside diameter of the previously inserted casing at a large value. For this reason, the inside diameter of the oil bore dug near the land surface needs to be large, resulting in increase of oil-well drilling cost.
A solution to the problem is disclosed in TOKU HYOU HEI. 7-507610. In the solution, a casing made of malleable material is inserted into a bore hole dug in the earth, and the casing is radially expanded and pressed against the bore hole wall by expanding a hydraulic expansion tool placed within the casing.
Another solution is disclosed in WO 98/0062. In the solution, a steel pipe, which is made of malleable steel of the type which exhibits strain hardening without yielding necking and ductile fracture, is inserted into a bore hole or a casing previously inserted, and the casing is radially expanded by use of a mandrel with a tapered face, made of nonmetallic material.
Those solutions of TOKU HYOU HEI. 7-507610 and WO98/0062 allow the insertion of the inside casing of which the outside diameter is smaller than the inside diameter of the bore hole or the outside casing. Therefore, a smooth insertion work of the inside casing is secured.
In those techniques, the inside casing, which is inserted into the bore hole or the outside casing, is radially expanded by use of a hydraulic expansion tool or a mandrel. Therefore, almost the entire cross sectional area of the bore hole may be utilized for transporting crude oil. Further, the effective cross sectional area of the bore hole is increased in those techniques. With this feature, the inside diameter of the bore hole to be dug may be reduced, leading to reduction of digging cost.
Furthermore, as disclosed in TOKU HYO HEI. 7-507610, when the casing is radially expanded and pressed against the bore hole wall, the casing is firmly held by compression stress induced by the bore hole wall. Therefore, there is no need of cement work.
As described above, the casing used for the oil well is considerably long, reaching to several thousands meter, and indispensably includes the bonding portions, However, those are no taken into consideration in TOKU HYO HEI. 7-507610 and WO 90/0062.
When the metal pipes are bonded into a metal-pipe bonded body by the welding bonding method or the metallurgical bonding method, such as the diffusion bonding method, the heating during the bonding process causes a heat affected portion to occur. In this state, a deformability of the bonding portion possibly reduces, and therefore the bonding portions may be cracked when the resultant metal-pipe bonded body is radially expanded by use of a mandrel.
When the metal pipes are bonded into a metal-pipe bonded body by the screw connecting method, and the resultant metal-pipe bonded body is radially expanded by a mandrel, a plastic deformation caused at the time of the expanding of the bonded body loosens the screw-bonded portion, resulting in the air-tightness at the bonding portion.
Illustration useful in explaining the screw connecting method is given in FIG.
7
. As shown, outside threads
1
a
and
2
b
are formed the outer surfaces of the end portions of metal pipes
1
and
2
. Those metal pipes are bonded together by means of a joint
7
having an inside thread
7
a.
The bonding portion of the metal-pipe bonded body is thicker than the non-bonding portion. When the metal-pipe bonded body thus configured is radially expanded by use of a mandrel, a deformation resistance at the bonding portion is increased, impeding the pipe expanding work.
When a metal-pipe bonded body of sev

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